Abstract
We measured the electric fields induced by figure-of-eight coils in homogeneous and inhomogeneous volume conductor models. Each model consisted of two troughs separated by a sheet of cellophane. In the inhomogeneous model, one of the two troughs was filled with 0.9% saline solution, and the other with 0.1% saline solution. In the homogeneous model, both troughs were filled with 0.9% saline solution. The figure-of-eight coil was held beneath the troughs with its wings parallel to a boundary between the two troughs. In the inhomogeneous model, the electric field along the boundary and especially its first spatial derivative were markedly elevated in comparison with the corresponding values recorded in the homogeneous model. The response of a nerve fiber to magnetic stimulation in an inhomogeneous medium is different from that in a homogeneous medium.
